Fig. 2

a Temporal behavior of Cr6+ and Cu2+ and corresponding change in the pH value at pH 2; b Cyclic voltammograms of CC electrode in Cu2+, Cr6+, and Cr6+ & Cu2+ mediated solution at pH 2
a Temporal behavior of Cr6+ and Cu2+ and corresponding change in the pH value at pH 2; b Cyclic voltammograms of CC electrode in Cu2+, Cr6+, and Cr6+ & Cu2+ mediated solution at pH 2